Claire I really like this, including the tight cropping. The layout of the 3 CDs is visually interesting, and the "rainbow effect" adds further interest. Obviously it's on topic, without overdoing it (seems to me).
I was going to say as a slight crit that the left hand diagonal rainbow takes the eye away out of the picture, but I've just checked again and actuallyit leads you right to the edge of the CD which takes you round to the right again. So pretty darn good, I'd say!